This invention relates to the structure and operation of DC--DC power converters.
Basically, a DC--DC power converter has a pair of input terminals for receiving an input voltage at one level, and it has a pair of output terminals on which it generates an output voltage at another level. Such a converter is used in many types of electronic equipment, like digital computers and their peripherals for example, to provide whatever voltages are needed by the circuitry from which the electronic equipment is made.
One very important characteristic of a DC--DC power converter is the efficiency with which it converts the input voltage to the output voltage. Efficiency is defined as P.sub.o .div.P.sub.i where P.sub.i is the power into the converter, and P.sub.o is the power out of the converter. Increasing efficiency makes the converter more economical to operate. Increasing efficiency also reduces the manufacturing cost of converter by lowering the need for high power components and high power cooling mechanisms such as fans and heat sinks.
Another important characteristic of a DC--DC power converter is the range of voltages and power levels over which the converter can operate. A wide range of output voltages is desirable since there are many types of electronic equipment which have different operating voltage requirements. Likewise, the power requirements of electronic equipment varies over a wide range. Further, input voltages from a battery power source often range from 12 volts to 50 volts; and input voltages from a rectified A-C power source often range from 160 volts to 300 volts.
Still another important characteristic of a DC--DC power converter is the cost at which it can be manufactured. Here a dilemma occurs because producing a converter which operates over a wide range of input voltage, output voltage, and power levels has required a wide range of components which in turn increases manufacturing cost. For example, multiple transformers having different turns ratios have been used in prior art converters to meet the different input voltage - output voltage requirements. Such multi turn transformers are, however, costly to manufacture.
Several examples of state of the art DC--DC power converters are disclosed in the "Linear Integrated Circuits Databook" by Unitrode Integrated Circuits, Inc. of Merrimack, N.H., 1987. There, the disclosed converters achieve a maximum efficiency of 75%, and they use multiturn transformers to get a desired input voltage to output voltage ratio. See pages 9-173 and 9-168.
Accordingly, a primary object of the invention is to provide a DC--DC power converter having a novel structure which in comparison to the prior art operates at a higher efficiency, operates over a wider range of voltage levels and power levels, and is less expensive to manufacture.